Because clogged gutters and downspouts can cause rain water to over-flow the gutter and promote damage to buildings and foundations, and, in fact, defeat the very purpose of installing gutters in the first place, there have been any number of attempts to prevent the entry of debris into the guttering system. Most common of these attempts is the installation of a screen, wire mesh or expanded metal or plastic mesh over the top of the gutter; this method, though effective against sizeable leaves and/or twigs, fails miserably in dealing with pine or fir needles. In those geographical areas where pine and fir trees are numerous the needle, itself, in conjunction with screen or mesh become a primary problem; as the needle becomes ensnared in the screen or mesh cover it, in turn, becomes a trap for more needles and leaves, and, ultimately, builds into a dam of its own and prevents rain water from entering into the drain gutters.
Other methods have been proposed, particularly U.S. Pat. Nos. 4,616,450; 4,604,837; 4,455,791; and 4,435,925 which, essentially, provide a solid cover for the gutter and depend upon the surface tension of the rain water to follow the contour of the cover around an edge and into some sort of opening into the gutter. These methods may be effective in preventing the entry of debris into the system but would only handle moderate water flow, in major rain storms the water quantity and velocity would tend to over-flow the gutter guard, again defeating the original purpose of installing the gutters in the first place.
U.S. Pat. No. 4,418,504 covers a solid type of guard with uniquely designed "reverse" water flow entry holes in the top of the guard. Though much thought must have gone into this and conceding the fact that it would probably be effective in preventing most debris entry into the system, it, too, would have the same limitations as to the amount of rain water that it would handle; it may be effective in minor rain storms but would be woefully inadequate in handling the quantity and velocity of rain water in a major storm.